Method for the control of a power-loom yarn feed device

ABSTRACT

The invention relates to a method for the control of a power-loom yarn feed device, whereby a drive motor for a rotating winding element is accelerated, decelerated or stopped, on demand, for yarn storage and, in order to avoid slack yarn during the stopping of the motor, the motor is independently driven slowly during a crawl phase, such that the motor is first stopped and then after stopping is slowly rotated in the crawl phase.

[0001] The present invention relates to a method according to thepreamble part of claim 1.

[0002] According to a method known from EP 05 80 267 A the drive motorof the yarn feeding and measuring device first is strongly deceleratedto the low speed of the crawl phase and then is rotated further at slowspeed for a predetermined rotation angle or a predetermined timeduration and then is stopped at the end of the crawl phase to preventthe formation of loops in the yarn between the storage bobbin and thewinding element. The strong deceleration of the drive motor and theinertia of the yarn result in a relaxation of the yarn between thestorage bobbin and the winding element which relaxation may lead to aloop formation. This danger is particularly high when the drive motor isdecelerated very strongly from high or maximum speed. During thesubsequent restart of the drive motor depending on consumption the yarnis stretched abruptly which might cause a yarn breakage. The crawl phasedirectly continuing the deceleration phase either prevents that a loopwill be formed or stretches an already formed loop.

[0003] According to the method known from EP 02 61 683 A a crawl phasedirectly continues a deceleration of the drive motor of the yarn feedingdevice down to crawl speed which crawl phase then is carried on for e.g.200 ms. The purpose of the crawl phase is to prevent the occurrence ofkinks in the yarn between the winding element and the storage surface,or to suppress slackness of the yarn in this area which may be caused bya backturn motion of the winding element counter to the normal windingdirection.

[0004] Both known methods are based on the task either to suppress aloop formation occurring with the deceleration of the drive motor or toremove a loop already prior to the stop of the winding element. Thecrawl phase conventionally is controlled by a software pre-adaptation ofthe control device, however, by doing so it may be complicated todetermine the start of the crawl phase precisely enough with the stillrunning drive motor, since the drive motor may have differing run outphases depending on the operational conditions and the yarn quality,respectively. To assure that during the crawl phase a sufficient yarnlength is pulled into the yarn feeding device, the crawl phase isadjusted for security reasons longer than necessary. For weavingmachines operating with high insertion frequencies and extremely highyarn speeds in the yarn feeding device, however, it is important to stopthe drive motor as rapidly as possible, in case that the number ofwindings stored in the yarn feeding device reaches the maximum and whenat the same time no yarn consumption takes place. A crawl phase, which,however, is too long for safety reasons easily may result in anoverfilling of the yarn feeding device. The static friction to start theyarn from stand still must be overcome in any case for a re-start andalso the static start friction in the drive motor.

[0005] It is an object of the invention to provide a method of the kindas disclosed at the beginning which allows a correct yarn control at theinlet side of a weaving machine yarn feeding device in a simple anddifferent manner.

[0006] Said object can be achieved by the features of claim 1.

[0007] The invention is considering the recognition that a relaxation ofthe incoming yarn during deceleration of the drive motor first neitheris particularly critical for the yarn nor for the yarn feeding device orthe weaving machine downstream of the yarn feeding device, but only iscritical for the subsequent re-start. The yarn relaxation occurs due tothe inertia or the elasticity of the yarn. Bearing this recognition inmind, the crawl phase for a predetermined rotation angle or apredetermined time duration thus is carried out after the stand stillcondition and so to speak in peace. For that reason, according to themethod, first the drive motor is brought to stand still completely, andparticularly because of the danger of an overfilling as rapidly aspossible, and then the time duration available between the stand stillcondition and the subsequent re-start depending on consumption isutilised to carry out the crawl phase for the precise time duration orthe exactly needed rotation angle, respectively. This is simpler interms of control technique. Experience has namely proven that always asufficiently long time duration will be available after the drive motorhas been stopped from high speed. A yarn relaxation is toleratedintentionally, which might be caused by inertia, by a backturn motion ofthe winding element due to the yarn tension, or for other reasons, inorder to first assure a rapid stop of the drive motor and to avoidoverfilling of the yarn feeding device, and a measure is started firstat a later point in time to omit the potential dangers of a formed loopwhich was particularly dangerous for the subsequent re-start.

[0008] According to the method the crawl phase is carried out for apredetermined time duration and with a predetermined speed timewisebetween a stand still depending on consumption and the subsequentre-start also depending on consumption or yarn demand. In this case thecrawl phase speed either may be constant or variable.

[0009] Particularly, the weaving pattern during a multi-colour weavingoperation may dictate longer stop pauses for a yarn feeding devicefeeding a certain colour. In the case that the yarn tends to relaxduring a longer pause, e.g. by pulling back the winding element counterto the normal winding direction, it may be expedient to associate thecrawl phase timewise not to the braking phase but to the re-start, i.e.,to carry out the crawl phase first immediately prior to the subsequentre-start such that a correct yarn control is guaranteed when the drivemotor is re-started.

[0010] In this case it may be expedient to adjust the timewisetermination of the crawl phase exactly to the point in time or evenshortly after the point in time of the subsequent restart. This mayresult in the advantage that the incoming yarn still may be in motionduring the subsequent re-start and has not reached a condition in whichthe yarn or the winding element, respectively, has to overcome staticstarting friction. A sliding transition from the crawl phase withoptionally increasing speed into the subsequent restart is particularlyadvantageous for delicate yarn qualities. In this case no staticstarting friction has to be overcome in the drive motor as well suchthat the drive motor may accelerate more forcefully.

[0011] The re-start phase of the drive motor basically may contain theprevious crawl phase in order to fully accelerate without stand stillalready from the crawl phase speed. Such a combined re-start phase e.g.is triggered by the consumption depending start signal for the drivemotor and is then made by a corresponding control routine. In this casethe crawl phase does not need to be controlled separately. There is nostatic starting friction which has to be overcome. The drive motor canbe accelerated more efficiently.

[0012] Basically it is expedient to know the point in time of thesubsequent and consumption depending re-start in order to preciselyadapt the crawl phase thereto. This is achieved according to a furthervariant of the method by providing weaving pattern dependent informationand to transmit the same to the control device, the informationindicating at which point in time or at which rotation angle value, e.g.of the driving shaft of the weaving machine or after how many upcominginsertion cycles the driving motor of this yarn feeding device again hasto re-start. On the basis of this information the crawl phase can becarried out precisely and optimally, particularly also such that asliding transition will take place from the crawl phase into theconsumption depending subsequent re-start.

[0013] By this pre-information of the control device of the yarn feedingdevice a prerequisite is set for adjusting the timewise termination ofthe crawl phase even shortly before, precisely on or shortly after thepoint in time at which the consumption depending subsequent re-startwill take place. This allows not only to effect a sliding transitioninto the subsequent re-start, but even allows to adjust the crawl phaseprecisely such that then only so much yarn is pulled into the yarnfeeding device sufficient to compensate for a potential loop formation.

[0014] Embodiments of the object of the invention will be explained withthe help of the drawings. In the drawings is:

[0015]FIG. 1 a schematic view of a yarn processing system which includesas basis components a yarn store, a weaving machine—feeding device and aweaving machine,

[0016] FIGS. 2-4 speed/time diagrams related to the control operation ofthe yarn feeding device in different variants of the method.

[0017] A yarn processing system S includes in FIG. 1 a yarn store 1,e.g. a storage bobbin, for a yarn Y wound on the storage bobbin, a yarnfeeding device F which pulls off the yarn Y from the yarn store 1 andintermediately stores the yarn in windings, and a yarn processingtextile machine, e.g. a weaving machine W in the form of a gripperweaving machine or a projectile weaving machine or an air jet weavingmachine or a water jet weaving machine, into the weaving shed 2 of whichthe yarn Y intermittently is inserted as the weft yarn during subsequentdiscrete insertion cycles. FIG. 1 only shows one yarn feeding device F.However, several yarn feeding devices F may be functionally associatedto the weaving machine W which several yarn feeding devices F may beoperated according to a predetermined sequence or depending from theweaving pattern.

[0018] The yarn feeding device F contains in a housing 3 an electricdrive motor M for a winding element 4. In the figure the incoming yarn Yis entering the winding element 4 from the left side and substantiallylinearly. The winding element 4 deflects the yarn Y outwardly andintermediately stores the yarn Y in adjacent yarn windings on a storagebody 5. In the shown embodiment of the yarn feeding device the storagebody 5 is provided stationarily. The yarn, optionally via a centralwithdrawal eyelet Ö, is withdrawn from the storage body 5 by a not showninsertion device of the weaving machine W. Instead the yarn feedingdevice may be provided with a rotatably driven storage body. Thisrespective yarn feeding device F is intended for use at a gripperweaving machine or a projectile weaving machine, or may be designed as ameasuring-feeding device for an air jet weaving machine or a water jetweaving machine, respectively.

[0019] An electronic control device C is associated to the drive motorM, and e.g. is arranged in housing 3. The control device C is connectedto sensors 6 sensing the number of windings or the size of theintermediate store on the storage body 5 and transmitting correspondingsignals to the control device C which re-starts the electric motor Mconsumption depending or depending on yarn demand. The control device Caccelerates the drive motor, controls a predetermined speed, deceleratesor even brakes and stops the drive motor and keeps the drive motorstopped during consumption depending on resting periods. As soon as thenumber of windings on the storage body 5 reaches a predetermined maximumvalue while the drive motor runs at maximum speed in a predeterminedwinding direction, the number of windings is detected by the frontsidesensor. Then the drive motor has to be stopped as rapidly as possible.In case that, due to consumption, the number of windings on the storagebody 5 drops below a predetermined number, the other sensor respondssuch that the control device C either accelerates the still runningdrive motor M or accelerates the drive motor M from stand still and witha predetermined characteristic of the acceleration or the re-start,respectively. Furthermore, the control device C may be programmed suchthat it subsequently adjusts a substantially continuous speed of thedrive motor just sufficient to continuously replenish the consumption bythe weaving machine W without stand still periods. In case of aso-called multi-colour weaving process with several yarn feeding devicesF there might be frequently longer stand still periods for some of theyarn feeding devices depending on the weaving pattern.

[0020]FIG. 1 indicates a control assembly C1 which may be associated tothe weaving machine W and which provides weaving pattern dependinginformation which, expediently, may be transmitted to the control deviceC of the yarn feeding device. Such information e.g. may indicate therespective yarn feeding device F that after expiration of apredetermined time or a number of insertion cycles after transmission ofthe information no further consumption or new consumption will takeplace for a predetermined time or during a predetermined number ofinsertion cycles. Then the control device C may, in order to avoidabrupt condition changes in the yarn feeding device, which could bedangerous for the yarn, carry out a special preparatory control of thedrive motor M. In case that the transmitted information indicates thatthe yarn feeding device will be taken out of consumption in a shortwhile, then the control device may already lower the still high speed ofthe drive motor in advance in order to avoid a later abrupt stop. Incase that the information indicates when again strong consumption and inconnection therewith a re-start under full acceleration is to beexpected, then the control device may start the drive motor with slowspeed and in advance to avoid a later sharp re-start jerk. It is furtherpossible to use the transmitted pre-information to preparatorilyincrease or decrease the running speed of the running drive motor.

[0021] During the run of the drive motor M particularly at high runningspeed, the yarn Y substantially is pulled from the yarn store 1 linearlyand runs in stretched condition into the winding element 4. When aresponse of the frontmost sensor 6 rapidly stops the drive motor M, e.g.because the number of yarn windings has reached the maximum allowablevalue, then the drive motor M will be forcedly braked to stop such thatthe maximum value will be exceeded as little as possible. Due to inertiathe incoming yarn Y from the bobbin then may relax during the stopprocedure such that it forms a loop L e.g. between the yarn store 1 andthe winding element 4. A slack yarn section also may be produced betweenthe winding element 4 and the storage body 5. After the drive motor stopthe tension present in an elastic yarn may turn back the winding element4 until the yarn will be relaxed as well. As soon as at a later point intime the drive motor re-starts depending on yarn consumption, such aslack yarn again will be stretched abruptly which easily results in ayarn breakage. Another danger is that loops or kinks formed due to therelaxation of the yarn during the stand still period will be transportedinto the windings on the storage body 5 and further even into theweaving shed 2 of the weaving machine.

[0022] To avoid such malfunctions a crawl phase with low speed iscontrolled during the stand still phase for the drive motor by thecontrol device C. The crawl phase is characterised in that the drivemotor is rotated at very low and constant, at varied or at increasingspeed during a predetermined time duration or over a predeterminedrotation angle of the winding element 4 in winding direction to reliablystretch out relaxed sections of the yarn Y between the storage 1 and thestorage body 5 or to even intentionally build-up a predetermined yarntension in those sections, respectively.

[0023] According to the invention, however, the crawl phase iscontrolled in FIG. 2 first after the true stop of the drive motor M andof the winding element 4. The crawl phase even may be associated to theupcoming consumption depending subsequent re-start of the drive motor M.

[0024] A curve 6 shown in FIG. 2 (speed/time diagram or weaving machinerotation angle diagram) represents the run of the drive motor M at highspeed before the control device C emits at a point in time t1 a commandfor a stop, e.g. because the frontmost sensor 6 has responded. Due toinertia the drive motor M or the winding element 4, respectively, thenstop at point in time t2. At point in time t3 after t2 the crawl phaserepresented by a curve 8 is controlled such that the crawl phase extendsover a predetermined time duration (from t5 to t4) or over apredetermined rotation range of the winding element 4. The crawl phaseis made with slow speed, preferably with essentially constant orslightly varied speed. As soon as the crawl phase is terminated at pointin time t4, the consumption depending subsequent re-start of the drivemotor, e.g. with strong acceleration, occurs at point in time t5 (curve7). A loop L in the yarn occurring earlier at point in time t2 or t3then is removed during the crawl phase such that a correct yarn controlwill be possible during the subsequent re-start.

[0025] The control the control device C may set a predetermined timeduration (t1 to t3) after the initiation of the crawl phase and at thepoint in time t1 of the stop signal, or the control device C may set acorresponding rotation angle range of the main shaft of the weavingmachine W, respectively. The respective time duration or the rotationangle range is selected such that the individual deceleration propertyof the drive motor and the winding element and other components rotatingtherewith will be considered such that the crawl phase first startsafter the true stop of the drive motor at point in time t2. It may beexpedient to adjust the end (point in time t4) of the crawl phase closeto the consumption depending subsequent re-start (point in time t5) toremove any relaxation of the yarn, even relaxations which occurredduring a longer stand still phase. The indirect triggering action forthe crawl phase is the stop signal emitted at point in time t1.Alternatively, the crawl phase could be controlled even by a cyclegenerator including a counter or by a clock. In case that the yarnfeeding device is operating relatively regularly with stand stillperiods of essentially equal durations, the control device C could carryout the crawl phase (curve 8) within each stand still period and bycorresponding software preparation such that the prerequisites e.g. asshown in FIG. 2 will be fulfilled.

[0026] In FIG. 3 the crawl phase represented by the curve 8 isintegrated into the motor re-start phase such that a sliding transitionis achieved from the crawl phase into a strong re-start acceleration. Inthis case the re-start phase of the drive motor M is set by the controlsuch that upon occurrence of the start signal for the drive motor atpoint in time t5 automatically first the crawl phase, optionally withincreasing speed, is carried out and that with a sliding transitionfurther acceleration is controlled starting at point in time t6 withoutan immediate stop. In this case no static starting friction of the yarnand no starting friction torque for the drive motor during the re-starthave to be overcome. In other words, to the benefit of the crawl phasethe strong re-start acceleration is somewhat delayed after point in timet5.

[0027] Stand still periods may have different time durations dependingon consumption. For that reason and according to FIG. 4 (and asexplained for control arrangement C1 in FIG. 1) information may betransmitted at a point in time t6 to control device C, e.g. from acontrol system monitoring the weaving pattern, that yarn consumptionwill cease in a short time, and that then at a later point in time t5 orshortly after t5 again yarn consumption will start from the feedingdevice. On the basis of this information defining the stand still phasethe control device C is able to control the crawl phase such that it iscarried out within the stand still period e.g. close to point in time t5for the consumption depending re-start and such that the crawl phaseeither is completely carried out until then or will terminate directlyat point in time t5 or even terminates with its final phase t4″overlapped with point in time t5. In both just described cases the yarnhas not stopped when the drive motor re-starts (sliding transition).This means that the yarn is treated tenderly or that the drive motor canbe accelerated more efficiently, respectively.

[0028] To correctly adjust the crawl phase the control device afterhaving received the pre-information may calculate e.g. the point in timet3 (if needed even also t4′, t4″) substantially at point in time t1 andthen controls the crawl phase accordingly.

[0029] In each case the drive motor M and the winding element 4 firstare truly stopped at point in time t2, prior to initiating the crawlphase. This may be made according to routine with the help of the stopsignal at point in time t1 or with the start signal at point in time t5,or individually on the basis of the pre-information.

1. Method for controlling a weaving machine yarn feeding device (F),having a drive motor (M) for driving a rotatable winding element (4) ina predetermined winding direction, which winding element (4) pulls off ayarn (Y) from a yarn storage (1) and winds the yarn (Y) into adjacentwindings on a yarn storing body, according to which method the drivemotor (M) is accelerated, decelerated or stopped by a control device (C)depending on the yarn consumption from the windings on the storage body,the drive motor when controlled to stop being further driven at slowspeed independent from yarn consumption in winding direction during acrawl phase for a predetermined time duration or over a predeterminedrotational angle to remove a previously occurred yarn relaxation (L)from the yarn (Y) between the yarn storage (1) and the storage body (5),characterised in that the drive motor (M) first is truly stopped at apoint in time (t2), and that the crawl phase (8) is initiated after thepoint in time (t2) of the stop in timewise or rotational angle relatedassociation either to the point in time (t2) of the stop or to the yarnconsumption depending point in time (t5) of the re-start of the drivemotor (M), respectively.
 2. Method as in claim 1, characterised in thatthe crawl phase is carried out by the drive motor (M) after a true stopat point in time (t2) and prior to the consumption depending subsequentre-start at point in time (t5).
 3. Method as in claim 1, characterisedin that the crawl phase is carried out by the drive motor firstimmediately prior to the point in time (t5) of the consumption dependingsubsequent re-start (t5).
 4. Method as in claim 1, characterised in thatthe timewise end (point in time t4, t4′, t4″) of the crawl phase isadjusted exactly at or shortly after the point in time (t5) of theconsumption depending subsequent re-start.
 5. Method as in claim 1,characterised in that the crawl phase is carried out by the drive motor(M) with the crawl phase directly continuing into the re-start
 6. Methodas in at least one of the preceding claims, characterised in thatweaving pattern depending information either for at least severalinsertion cycles without any yam consumption or for subsequent insertioncycles with yam consumption is provided in advance, that saidinformation is transmitted to the control device (C), and the controldevice initiates the crawl phase (8) prior to or exactly at theconsumption depending subsequent re-start of the previously stoppeddrive motor (M) on the basis of the transmitted information.
 7. Methodas in claim 6, characterised in that the timewise or rotation anglerelated end (point in time t4, t4′, t4″) of the crawl phase either isset shortly prior to, exactly at, or shortly after the point in time(t5) or the rotation angle value of the consumption depending subsequentre-start of the drive motor (M).